팬더 데이터 프레임이 1 개만 선택했을 때 2 개의 열을 반환하는 이유 [중복]

Question

matplotlib로 일부 플롯을 만드는 동안 pandas의 이상한 동작을 발견했지만 열을 1 개만 선택하면 2가 반환됩니다.

import pandas as pd
import io

data = io.StringIO("""time_0,1,time_1,2,time_2,0,time_3,3
-0.002,-0.1225,-0.002,-0.0904,-0.002,0.0331,-0.002,0.,
0.0,-0.1225,0.,-0.0904,0.,0.0331,0.,0.,
0.002,-0.1224,0.002,-0.0904,0.002,0.0331,0.002,0.,
0.004,-0.1225,0.004,-0.0904,0.004,0.0331,0.004,0.,""")

df = pd.read_csv(data)
print(df["time_0"])

산출:

-0.002 -0.1225
0.000 -0.1225
0.002 -0.1224
0.004 -0.1225
이름 : time_0, dtype : float64

"time_0"및 "1"열의 값을 모두 표시하지만 "time_0"만 선택되었습니다. 버그입니까, 기능입니까?

Answer 1

데이터 프레임은 한 줄만 반환하지만 "1"열과 동일한 인덱스를 먼저 표시합니다.

df
Out[3]: 
        time_0      1  time_1      2  time_2      0  time_3   3
-0.002 -0.1225 -0.002 -0.0904 -0.002  0.0331 -0.002     0.0 NaN
 0.000 -0.1225  0.000 -0.0904  0.000  0.0331  0.000     0.0 NaN
 0.002 -0.1224  0.002 -0.0904  0.002  0.0331  0.002     0.0 NaN
 0.004 -0.1225  0.004 -0.0904  0.004  0.0331  0.004     0.0 NaN

의도하지 않게 첫 번째 열을 인덱스로 사용하는 것처럼 보입니다 ... ,각 줄 의 추가 로 인해 마지막 열을 nan 값으로 사용합니다 ....

제거해보십시오 ,:

 import pandas as pd
 import io
 
 data = io.StringIO("""time_0,1,time_1,2,time_2,0,time_3,3
 -0.002,-0.1225,-0.002,-0.0904,-0.002,0.0331,-0.002,0.
 0.0,-0.1225,0.,-0.0904,0.,0.0331,0.,0.
 0.002,-0.1224,0.002,-0.0904,0.002,0.0331,0.002,0.
 0.004,-0.1225,0.004,-0.0904,0.004,0.0331,0.004,0.""")
 
 df = pd.read_csv(data)
 print(df["time_0"])

이 코드는 인쇄됩니다

0   -0.002
1    0.000
2    0.002
3    0.004
Name: time_0, dtype: float64